Broadcaster cut international lines (5)
I believe the answer is:
radii
'lines' is the definition.
(radius is a kind of line)
'broadcaster cut international' is the wordplay.
'broadcaster' becomes 'radio' (I've seen this before).
'cut' means to remove the last letter.
'international' becomes 'i' (abbreviation eg in IMF).
'radio' with its last letter taken off is 'radi'.
'radi'+'i'='RADII'
(Other definitions for radii that I've seen before include "They meet in the middle of a circle" , "Two making up diameter" , "Lines from centre to perimeter of a circle" , "Forearm bones: spokes" , "Centre-circumference lines" .)